fix eslint errors

src/compiler/program.ts

@@ -814,7 +814,7 @@ namespace ts {
         // We set `structuralIsReused` to `undefined` because `tryReuseStructureFromOldProgram` calls `tryReuseStructureFromOldProgram` which checks
         // `structuralIsReused`, which would be a TDZ violation if it was not set in advance to `undefined`.
         let structuralIsReused: StructureIsReused | undefined;
-        structuralIsReused = tryReuseStructureFromOldProgram();
+        structuralIsReused = tryReuseStructureFromOldProgram(); // eslint-disable-line prefer-const
         if (structuralIsReused !== StructureIsReused.Completely) {
             processingDefaultLibFiles = [];
             processingOtherFiles = [];

src/compiler/scanner.ts

@@ -2225,17 +2225,17 @@ namespace ts {
         const size = str.length;
         // Account for out-of-bounds indices:
         if (i < 0 || i >= size) {
-          return undefined!; // String.codePointAt returns `undefined` for OOB indexes
+            return undefined!; // String.codePointAt returns `undefined` for OOB indexes
         }
         // Get the first code unit
         const first = str.charCodeAt(i);
         // check if it’s the start of a surrogate pair
         if (first >= 0xD800 && first <= 0xDBFF && size > i + 1) { // high surrogate and there is a next code unit
-          const second = str.charCodeAt(i + 1);
-          if (second >= 0xDC00 && second <= 0xDFFF) { // low surrogate
-            // https://mathiasbynens.be/notes/javascript-encoding#surrogate-formulae
-            return (first - 0xD800) * 0x400 + second - 0xDC00 + 0x10000;
-          }
+            const second = str.charCodeAt(i + 1);
+            if (second >= 0xDC00 && second <= 0xDFFF) { // low surrogate
+                // https://mathiasbynens.be/notes/javascript-encoding#surrogate-formulae
+                return (first - 0xD800) * 0x400 + second - 0xDC00 + 0x10000;
+            }
         }
         return first;
     };

src/compiler/transformers/declarations.ts

@@ -83,7 +83,7 @@ namespace ts {
         let currentSourceFile: SourceFile;
         let refs: Map<SourceFile>;
         let libs: Map<boolean>;
-        let emittedImports: readonly AnyImportSyntax[] | undefined; // must be declared in container so it can be `undefined` while transformer's first pass
+        let emittedImports: ReadonlyArray<AnyImportSyntax> | undefined; // must be declared in container so it can be `undefined` while transformer's first pass
         const resolver = context.getEmitResolver();
         const options = context.getCompilerOptions();
         const newLine = getNewLineCharacter(options);

src/services/codefixes/importFixes.ts

@@ -360,8 +360,8 @@ namespace ts.codefix {
             case ModuleKind.UMD:
                 if (isInJSFile(importingFile)) {
                     return isExternalModule(importingFile) ? ImportKind.Namespace : ImportKind.ConstEquals;
-                 }
-                 return ImportKind.Equals;
+                }
+                return ImportKind.Equals;
             case ModuleKind.System:
             case ModuleKind.ES2015:
             case ModuleKind.ESNext:

src/testRunner/unittests/tsbuild/watchEnvironment.ts

@@ -29,10 +29,10 @@ namespace ts.tscWatch {
                 solutionBuilder.build();
                 checkOutputErrorsInitial(system, emptyArray, /*disableConsoleClears*/ undefined, [
                     `Projects in this build: \r\n${
-                    concatenate(
-                        pkgs(index => `    * pkg${index}/tsconfig.json`),
-                        ["    * tsconfig.json"]
-                    ).join("\r\n")}\n\n`,
+                        concatenate(
+                            pkgs(index => `    * pkg${index}/tsconfig.json`),
+                            ["    * tsconfig.json"]
+                        ).join("\r\n")}\n\n`,
                     ...flatArray(pkgs(index => [
                         `Project 'pkg${index}/tsconfig.json' is out of date because output file 'pkg${index}/index.js' does not exist\n\n`,
                         `Building project '${project}/pkg${index}/tsconfig.json'...\n\n`
@@ -70,7 +70,7 @@ namespace ts.tscWatch {
                 system.writeFile(typing.path, `${typing.content}export const typing1 = 10;`);
                 system.checkTimeoutQueueLength(0);
 
-                function flatArray<T>(arr: T[][]): readonly T[] {
+                function flatArray<T>(arr: T[][]): ReadonlyArray<T> {
                     return flatMap(arr, identity);
                 }
                 function pkgs<T>(cb: (index: number) => T): T[] {